Cold exposure and hormonal secretion: A review

Low ambient temperature during winter seasons is typical for all circumpolar areas. This sets definite demands for every day life and work. Naked, man is quite helpless in polar winter, but he has been able to inhabit all corners of the ear th using technical developments in clothing and housing. Yet there are situations, especially in circumpolar areas, when bodily exposure to cold environment cannot be avoided. Homeothermic animals protect themselves from the cold by increasing heat production and decreasing heat losses. For practical reasons man has very few means of reducing heat loss by natural ways. Heat is produced by muscular work and by chemical reactions. Oxidative phosphorylation of dietary fuels such as carbohydrates and fats brings forward energy-rich phosphate compounds, at the same time liberating heat for bodily uses. Thyroid and adrenal hormones and the sympathetic nerve system maintain and regulate the oxidative phosphorylation that occurs mainly in the mitochondria of brown and white fat and skeletal muscle tissues. It is notewor thy that animals from which thyroid or adrenal glands are removed do not tolerate cold.